There is known an image monitoring system for enabling, by images captured by a camera, monitoring of a display state of products in a display shelf in a store.
However, in general, in this kind of system, store staff visually checks stockout, etc. of products.
Although there is known a system which recognizes products appearing in an image by an image process, this system is not suited to monitor the display state of products in a display shelf.
Under the circumstances, it is desired to efficiently acquire information for confirming the display state of products in the display shelf, from an image captured by photographing the display shelf.